Process for preparing oximinoacetone



Jan. 17, 1956 R CQRAOR 2,731,499

PROCESS FOR PREPARING OXIMINOACETONE Filed Feb. 5, 1954 ACETONE NITRITE MOLE RATIO CONVERSION (NITRITE BASIS) N (D O O 0.02 0.04 0.06 0.08 o.|o 0.12 0.14 016 0.8 0.20 HYDROCHLORIC ACID/ ISOPROPYLNITRITE WEIGHT RATIQ INVENTOR GEORGE R. CORAO R BY \%L%%- ATTORNEY 2,131,499 I M t PROCESS FOR PREPARING OXIMINOACETONE George R. Coraor, Woodbury, N. 1., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Application February 5, 1954, Serial No. 408,385 3 Claims: (Cl. 260-566) The present invention relates to an improved process for the preparation of oximinoacetone by the reaction of an alkyl nitrite with acetone.

A number of methods for preparing oximinoacetone have been reported in the literature. These methods include acidification of an aqueous solution of sodium nitroprusside and acetone", nitrosation and decarboxylation of ethyl acetoacetate, reaction of acetone with nitrosyl chloride, nitrosation of acetone with sodium nitrite and glacial acetic acid, and hydrochloric acid-catalyzed nitrosation of acetone with alkyl nitrites. Only the last of the portance. This method was reported by Claisen, Ber. 20, 252 (1887) and by Claisen and Marrasse, Ber. 22, 526 (1889). According to the above reports, conversions of less than 40% were obtained by heating to boiling equimolar quantities of acetone and the alkyl nitrite in the a presence of the acid catalyst. The product was thus ob-. tained in a very impure form, the loss in yield and the low purity being primarily due to the formation of methylglyoxal. Later investigators were unable to improve the described process. Thus, it is generally acceptedthat methyl groups are exceptionally ditficult to nitrosate by any method (Touster, Organic Reactions, John Wiley and Sons).

In view of the demand for 2,5-dimethylpiperazine as.

an intermediate in the preparation of polyamides and,

the utility of oximinoacetone as a starting material for the synthesis of 2,5-dimethylpiperazine, a highly efficient and economical process for the preparation of oximinoacetone is desirable.

It is, accordingly, an object of the present invention to provide an improved process for the preparation of oximinoacetone. A further object is to provide such process,

1 I use an alkyl nitrite having at least three carbon atoms.

In order to illustrate more fully the present invention, reference is made to the following examples which represent specific embodiments, the invention not being limited thereto.

EXAMPLE 1 To a stirred solution of 465 grams of acetone and 5,

milliliters of concentrated hydrochloric acid cooled in an ice bath, 178.4 grams of isopropyl nitrite was added dropwise. When the addition was completed, the isopropyl alcohol formed and the unreacted acetone were removed from the product under reduced pressure.

Oximiuoacetone weighing 164 g. (94% conversion, ni'

trite basis) with a melting point of 61-64 .Crwas obtained. Recrystallization from an ether-petroleum ether 25 above mentioned methods appears to be of practical im- *6 2,731,499 Patented Jan. 17, 1956 ice One half mole of isopropyl nitrite (44.6 g.) and 2.7 moles of acetone (156.4 g.) containing 5.9 g. of. HCl

were added simultaneously at measured, rates to a helixpacked vertical jacketed column which provided a retention timeiof approximately 20 seconds, the reaction mixture then entering an ice-cooled receiver. The column was maintained at approximately 13 C. Forty-two grams of crude oximinoacetone melting at 56-62 C. remained after distillation under reduced pressure, representing a conversion of 97% based on, the isopropyl nitrite introduced.

EXAMPLE 3 The following table illustrates the preparation of oximinoacetone by the reaction of isopropyl nitrite and acetone. In each case 44.6 grams of isopropyl nitrite (0.5 mole) was used, and the procedure followed was similar to that described in Example 1.

Table 1 Oxlminoacetone Acetone! H01 Acetone (mole) fig'gig nitrite, 8 3 Percent 1510 ratio (g.) conversion EXAMPLE 4 EXAMPLE 5 Seventy and one-half g. of isoamyl nitrite and 213 g. of acetone containing 14 ml. of concentrated HCl were added simultaneously over a period of 95 minutes to a packed reactor cooled to 20 C. The efiiuent was neutralized with concentrated aqueous ammonia and the ammonium chloride removed by filtration. After reduced pressure distillation, a good yield of oxirninoacetone containing residual isoamyl alcohol remained.

Figure 1 illustrates the eflect of temperature upon conversion and Figure 2 illustrates the efiect of the 'acetone/nitrite ratio on conversion. From these figures, it is apparent that the process is operative over a temperature range of from about 0 to 70 C., with optimum conversion being obtained between 0 and 30 C., and an acetone-nitrite mole ratio of at least 2 to 1. In the runs represented in each of the above figures, the hydroreactiontemperature was 13 C.

dlluric acid-isopropyl nitrite :ratio was 'ojfiand-the residence time was about twenty seconds. In the runs represented in Figure '1, the acetone/nitrite mole ratio was 4 to 1, and in the runs represented in Figure 2, the

Figure 3 illustrates the effect of cata-lyst concentration on the conversion obtained. The .runs represented in this figure were all madejat a 4 to 1 acetone/nitrite mole ratio and at a twenty second residence time. The points making the curve were obtained from runs made at 13 C. From this figure, it is apparent that a hydrochloric acidnitrite ratio .of at least 0.05 is required for satisfactory conversion. l

The use of the V at "least three carbonatoms; is highly advantageous be-' cause pressure is not required to maintain a liquid'phase reaction medium at the reaction temperatures, and be cause the higher alcohol-produced by the reaction does not form an azeotrope with acetone, thus, a reiadyaeparation of the productsis obtainable. "In the case of either ethyl'or methyl'riitrite, on the other hand; pressure'must be used to maintain a liquid phase reactin, the conditions of the reaction must be very carefully controlled,

particularly \vithcregard "to :contact time, in order to avoid decreased yields, and the products are .diflicult to sepa rate because of :azeotrope :formation. Residence time is not critical in the case of the higher alkyl nitrites.

The failure of the prior art to achieve satisfactory ;results in the preparation of oximinoacetone is believed primarily due to the failure to discover the critical nature higher alkyl 'nitrites, i. e., those *having mole of nitrite. As shown in both Figure 2 and the table of Example 3, at a mole ratio of 1.2 to 1, the conversion, based on the nitrite introduced, was only about 15%.

The present invention has been fully described in the foregoing. I intend, therefore, to be limited only by the following claims.

I claim:

1. A'PIOCQSS for producing .oxirninoacetone which comprises reacting an alkyl nitrite having at least three carbon atoms with acetone in the presence of a hydrochloric acid catalyst at atemperature between 0 and C., the mole ratio of the acetone to the alkyl nitrite being at least 2 to 1 and the weight ratio of the acid catalyst to the alkyl nitrite being at least 0.05 to 1. g

2. A process'for producingoximinoacetone which comprises reacting isopropyl nitrite with acetone in the presence of a hydrochloric acid catalyst at a temperature between 0 .and 30 C., the mole ratio of the acetone to the isopropyl nitrite being at least 2 to 1 and the weight ratio 7 of the acid catalyst to the isopropyl nitrite being at least 0.05 to .1.

3.,A process .as claimed .in claim 2,,wherein the isopropyl ,nitrite and an acetone-acid catalyst solution are reacted inta continuous flow process. 

1. A PROCESS FOR PRODUCING OXIMIOACETONE WHICH COMPRISES REACTING AN ALKYL NITRITE HAVING AT LEAST THREE CARBON ATOMS WITH ACETONE IN THE PRESENCE OF A HYDROCHLORIC ACID CATALYST AT A TEMPERATURE BETWEEN 0* AND 70* C., THE MOLE AND THE WEIGHT RATIO OF THE ACID CATALYST TO THE ALKYL NITRITE BEING AT LEAST 0.05 TO
 1. 